1. Field of the Art
The present embodiments relate to paper and paper making.
2. Description of Related Art
Paper is sheet material containing interconnected small, discrete fibers. The fibers are usually formed into a sheet on a fine screen from a dilute water suspension or slurry. Paper typically is made from cellulose fibers, although occasionally synthetic fibers are used.
Paper products made from untreated cellulose fibers lose their strength rapidly when they become wet, i.e., they have very little wet strength.
Wet strength resins applied to paper may be either of the “permanent” or “temporary” type, which are defined, in part, by how long the paper retains its wet strength after immersion in water.
Commercially available epichlorohydrin-based wet strength resins are typically prepared by reaction of epichlorohydrin in aqueous solution with polymers containing secondary amino groups. Not all of the epichlorohydrin in the aqueous reaction mixture reacts with the amine groups to functionalize the polymer. Some of the epichlorohydrin remains unreacted, some reacts with water to form 3-chloropropane-1,2-diol, and some reacts with chloride ion to form dichloropropanol, normally a mixture of 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol. These organic chloride by-products are generally considered to be environmental pollutants, and increasing environmental concerns have created an interest in wet strength resins that have reduced levels of such by-products. As a result, paper makers and chemical suppliers have been working to find alternatives to conventional epichlorohydrin-based wet strength resins with high levels of chloroorganic residuals, or to find alternative methods of reducing the levels of the epi by-products.
The description herein of certain advantages and disadvantages of known methods and compositions is not intended to limit the scope of the present disclosure. Indeed the present embodiments may include some or all of the features described above without suffering from the same disadvantages.